1. Field of Invention
The present invention relates to a real time monitoring and control system for combustion systems. More particularly, the invention concerns a real time monitoring and control system that utilizes a high sensitivity light sensor that monitors the flame of a single or multi-flame combustion system and produces an output that is proportional to the temperature of the flames, which is utilized in a feed-back control type system operating in real time to adjust the air fuel ratio of the flame to an optimum burning level.
2. Description of the Prior Art
Various systems exist in the prior art for monitoring combustion systems for the purpose of adjusting the combustion efficiency to an ideal figure, and/or to provide safety control of the combustion process. Many such safety systems utilize a detector which senses the presence or absence of the flame itself in the combustion chamber and produces a signal which can be utilized to shut down the burner should the flame extinguish. These systems provide adequate safety control but generally utilize a low sensitivity detector for monitoring the flame since all that is desired is to detect its presence or absence.
Other systems which adjust the combustion efficiency of the system utilize means for sensing the content of oxygen or other constituents in the flue gas and producing a single which can be utilized to control input parameters of the system, such as air fuel ratio, for example. It should be recognized that the use of an oxygen sensor in the exhaust or flue chamber of a combustion system may be adequate to sense the combustion characteristics of a single flame system, if adjustment to a combustion efficiency in the range of 4 to 8 percent of excess oxygen is satisfactory. However, due to the inherent time delay involved in monitoring oxygen content down-stream from the combustion chamber, wherein a large thermal mass or volume of gasses circulating within the furnaces usually requires up to several minutes between sensing temperature variations and correction thereof, changes cannot be affected with sufficient rapidity to control combustion efficiency to an excess oxygen state much lower than the 4 percent range with usual furnace conditions. Moreover, when it is desired to monitor and control a multi-flame system, the use of a down-stream oxygen monitor is less efficient since the oxygen monitor gives no indication whether one or more of the multiple flames are operating at optimum efficiency, i.e., it simply averages the efficiency of the multi-flame system.
Other combustion control systems utilize discrete temperature sensing devices such as thermocouples located within the combustion chamber itself as an indication of the efficiency of combustion. However, such systems have not been designed to provide better control efficiency than the oxygen monitoring type systems since the temperature sensing devices, as well, involve a response time which prevents real time adjustment of the flame. Moreover, it is difficult to arrange temperature monitoring devices of discrete type within the combustion so as to accurately measure the combustion temperature of more than one given position of a selected flame of a multi-flame system.
Accordingly, a need exists for a flame monitoring and control system which can provide real time monitoring of combustion temperature in a single or multi-fired system whereby the air fuel ratio of the system can be adjusted to the lowest possible excess oxygen level in order to optimize the efficiency of the system. Such a system, when applied to furnaces utilized for heating or other purposes could result in significant savings in fuel usage and operating costs. Moreover, it has been recently recognized that pollution control can be achieved through such a system since in the usual combustion process complete burning resulting in lower pollutant constituents occurs with maximum or close to maximum combustion efficiency. Consequently, such a system could be utilized to control sulphur dioxide, carbon monoxide and nitride pollutants, etc. Finally, a need exists to combine such a system with means for providing fail safe control over the combustion process in such large multi-fired furnaces.